Direct interaction of taste stimuli with ion channels mediates the transduction of several ionic taste stimuli. A major goal of the next funding period is to determine the role of K+ channels and amiloride-sensitive sodium channels in taste transduction in rats. The principal investigator will investigate whether the channels are located preferentially in apical or basolateral membranes and if they are distributed differentially in vallate and fungiform taste buds, which are innervated by different sensory nerves. Using a combination of patch- clamp recordings from isolated rat taste buds and loose-patch recording from rat taste buds in situ, the principal investigator will test the following hypotheses: (1) apically-located K+ channels, important in bitter and sour transduction, are located preferentially in vallate taste cells, while apically-located amiloride-sensitive Na+ channels, important in salt and sour transduction, are restricted to fungiform taste cells; (2) these distinctive distributions are determined by properties imposed by the innervating nerve fibers and not by properties inherent in the taste cells. The specific aims will address the apical/basolateral distribution of K+ channels and amiloride-sensitive sodium channels in fungiform and vallate taste cells, the role of apical and basolateral ion channels in taste transduction, and the role of specific neural innervation in the development and maintenance of amiloride-sensitive sodium and potassium channels. These proposed studies will provide important new information about the role of ion channels in salt, sour and bitter transduction in mammals, as well as the role of afferent innervation in specifying the expression of ion channels in taste cells.